Photocatalyst for removing hydroxypropyl guar gum in flow-back fluid of fracturing fluid and preparation method and use thereof

Abstract

The present invention relates to the photocatalyst field, and discloses a photocatalyst for removing hydroxypropyl guar gum in flow-back fluid of fracturing liquid, and a preparation method and the use of the photocatalyst, wherein, the photocatalyst is expressed by Bi 5 O 7 Br 0.5 I 0.5 , in a powder form in 12-15 nm particle size, with 285-300 m 2 /g specific surface area. The photocatalyst has improved response to visible light, has greater specific surface area, and has very high activity in removal of hydroxypropyl guar gum in flow-back fluid of fracturing liquid. In addition, the photocatalyst can be prepared with a simple preparation method under mild conditions, and can be used to remove hydroxypropyl guar gum in flow-back fluid of fracturing liquid.

The invention claimed is: 
     
       1. A photocatalyst for removing hydroxypropyl guar gum in flow-back fluid of fracturing fluid, expressed by Bi 5 O 7 Br 0.5 I 0.5 , in a powder form in 12-15 nm particle size, having 285-300 m 2 /g specific surface area. 
     
     
       2. The photocatalyst according to  claim 1 , wherein the particle size is 13-14 nm, and the specific surface area is 287-290 m 2 /g. 
     
     
       3. A method for preparing a photocatalyst for removing hydroxypropyl guar gum in flow-back fluid of fracturing liquid, comprising:
 (1) mixing a bismuth-containing compound, concentrated nitric acid and water to prepare solution A; 
 (2) preparing water solution B of bromine-containing compound and iodine-containing compound; 
 (3) adding the solution B into the solution A by dropwise adding under a stirring condition to have a first reaction; 
 (4) controlling a first product obtained in the step (3) to have a second reaction; and 
 (5) drying a second product obtained in the step (4). 
 
     
     
       4. The preparation method according to  claim 3 , wherein the molar ratio of the bromine-containing compound measured in Br to the iodine-containing compound measured in I to the bismuth-containing compound measured in Bi is 1:1:(3-15). 
     
     
       5. The preparation method according to  claim 3 , wherein the bismuth-containing compound is bismuth nitrate pentahydrate; the iodine-containing compound is potassium iodide and/or sodium iodide, the bromine-containing compound is potassium bromide and/or sodium bromide. 
     
     
       6. The preparation method according to  claim 3 , wherein the bismuth-containing compound is potassium iodide; the bromine-containing compound is potassium bromide. 
     
     
       7. The preparation method according to  claim 3 , wherein in the step (1), in relation to 1 mmol said bismuth-containing compound, the dose of the water is 10-50 mL, and the dose of the concentrated nitric acid is 2-5 mL. 
     
     
       8. The preparation method according to  claim 3 , wherein in the step (2), in relation to 1 mmol said compound, the dose of the water is 10-50 mL; and, in relation to 1 mmol said iodine-containing compound, the dose of the water is 10-50 mL. 
     
     
       9. The preparation method according to  claim 3 , wherein in the step (3), the conditions of the first reaction include: stirring for 10-40 min. at 50-100 rpm stirring rate, and the rate of dropwise adding is 1-2.5 mL/min. 
     
     
       10. The preparation method according to  claim 3 , wherein in the step (4), the conditions of the second reaction include: pressure: 10-15 MPa, temperature: 140-180° C., and time: 14-18 h. 
     
     
       11. The preparation method according to  claim 10 , wherein in the step (4), the conditions of the second reaction include: pressure: 12-14 MPa, temperature: 150-170° C., and time: 15-17 h. 
     
     
       12. The preparation method according to  claim 3 , wherein in the step (5), the conditions of the drying include: drying temperature: 60-80° C., and drying time: 5-24 h. 
     
     
       13. The preparation method according to  claim 12 , wherein in the step (5), the conditions of the drying include: drying temperature: 65-75° C., and drying time: 7-15 h.